Date: Thu, 2 Jul 2015 19:40:21 -0400 From: Ryan Stone <rysto32@gmail.com> To: abhishek kulkarni <abhya007@gmail.com> Cc: Ryan Stone <rstone@freebsd.org>, "freebsd-dtrace@freebsd.org" <freebsd-dtrace@freebsd.org> Subject: Re: Regarding schedgraph.d Message-ID: <CAFMmRNy0AFBazEKR=QFY1h6htTre=Zi=dd==2c7Dkfc7BygZ%2BQ@mail.gmail.com> In-Reply-To: <CAJUVseuHN-hLvLP6AQZdjwnQqpB24nSfm-dAWmn=j3y1EYiEMw@mail.gmail.com> References: <CAJUVsesOHQegeS=yfED8iKUoJK5KEVnLBqKH1MpSUuH_4i=_RQ@mail.gmail.com> <CAFMmRNwu8SoX-dJPb1wBh26UnXAnM5x7FZprDmXpVXbS7htkYQ@mail.gmail.com> <CAJUVseuHN-hLvLP6AQZdjwnQqpB24nSfm-dAWmn=j3y1EYiEMw@mail.gmail.com>
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The best that I can offer right now is the Illumos documentation: http://dtrace.org/guide/chp-sched.html The caveat is that the types documented there are not implemented in FreeBSD. Where illumos uses a lwpsinfo_t, FreeBSD uses a struct thread: https://svnweb.freebsd.org/base/head/sys/sys/proc.h?revision=284215&view=markup#l206 psinfo_t is replaced by struct proc. https://svnweb.freebsd.org/base/head/sys/sys/proc.h?revision=284215&view=markup#l495 cpuinfo_t* arguments are not implemented and passed as NULL. You can access the current cpu number using the "cpu" variable. Finally, the schedctl-* probes don't apply to the FreeBSD scheduler and therefore are unimplemented. On Thu, Jul 2, 2015 at 12:30 PM, abhishek kulkarni <abhya007@gmail.com> wrote: > Thanks Ryan. Those are some very useful tips. Ill get on with trying all > of those and get back If I have some more concerns. Also, could you be > having some document which has some logical description about the "sched" > probes for FreeBSD, which could give details like when is the particular > probe fired, the probe's arguments etc. Thanks again. > > Regards > Abhishek Kulkarni > > On Wed, Jul 1, 2015 at 1:51 PM, Ryan Stone <rysto32@gmail.com> wrote: > >> On Tue, Jun 30, 2015 at 7:11 PM, abhishek kulkarni <abhya007@gmail.com> >> wrote: >> >>> Hello Ryan, >>> >>> I was looking to schedgraph.d . I need to modify the script for a >>> single, particular thread. I atleast need to know the thread transitions, >>> as in the context switches for the particular thread and also the different >>> states for a single thread. Could you please help with the filters that I >>> need to add in order to use the script for a single thread or else suggest >>> me just the nexessary probes that I could use for writing a new script for >>> a single thread . >>> >>> Regards >>> Abhishek Kulkarni >>> >> >> There are a couple of things that you could filter on, depending on what >> you know about the thread of interest. The "execname" variable gives the >> name of the current process. If you're interesting in tracing a >> single-threaded process, that would be an option. Another variable of >> interest would be the "curthread" variable. This gives a pointer to the >> "struct thread" for the current thread. One field that you could trace on >> would be curthread->td_tid. You can use ps to find your thread id and then >> run the script as: >> >> dtrace -s script.d <tid> >> >> And in the script, filter with / curthread->td_tid == $1 /. Another >> field that you could use would be curthread->td_name, which contains the >> name of the current thread. If your application names threads with >> "pthreads_set_name_np()", then that name will appear in td_name and you can >> filter based off of that. >> >> An alternative approach would be to use a thread-local variable. If you >> know that your thread is the only thread that might hit a probe, you can >> set a thread local variable in that probe and filter on it later on. For >> example, if your thread is the only thread that will call a function called >> foobar() in the kernel, you could do this: >> >> fbt::foobar:entry >> { >> self->interesting = 1; >> } >> >> sched:::off-cpu >> / self->interesting / >> { >> /* trace interesting data here */ >> } >> >> >
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